Dental Outcomes After Medicaid Insurance Coverage Expansion Under the Affordable Care Act

IMPORTANCE Dental coverage for adults is a state option in Medicaid, and despite significant gains in coverage after the Medicaid expansion under the Affordable Care Act (ACA), dental outcomes among adults in expansion states remain unexplored. OBJECTIVE To explore the association of state coverage of dental benefits through Medicaid expansion with clinical dental outcomes. DESIGN, SETTING, AND PARTICIPANTS This cross-sectional study analyzed data from the National Health and Nutrition Examination Survey from 2009 to 2018. Included participants were low-income adults aged 19 to 64 years with income up to 138% of the federal poverty level. The study used a difference-in-differences analysis to compare changes from before to after ACA expansion in expansion states vs in control states. Changes were examined in the full sample and separately in states that did and did not provide Medicaid adult dental benefits. We defined a state as providing Medicaid adult dental benefits if it covered services beyond emergency dental benefits in 2014. Data were analyzed from November 2020 to March 2021. EXPOSURES Medicaid expansion under the ACA. MAIN OUTCOMES AND MEASURES Rates of health coverage, having a dental visit, affordability of dental care in the past year, poor oral health, and teeth flossing were obtained from self-reported data. Mean number of missing teeth and prevalence of untreated decayed teeth, filled teeth, and functional dentition were obtained from clinical examination data. RESULTS Among 7637 low-income adults, the mean (SD) age was 37.8 (13.4) years and 4153 (weighted percentage, 54.5 %) were women. At baseline, 1732 low-income adults in nonexpansion states compared with 2520 low-income adults in expansion states were more likely, as shown by weighted percentage, to be Black (473 individuals [21.0%]vs 508 individuals [15.1%]) and US born (1281 individuals [76.7%] vs 1613 individuals [69.6%]). In the full sample, Medicaid expansion, compared with nonexpansion, was associated with an increased rate of seeing a dentist in the prior year (12.4 percentage points; 95% CI 4.6 to 20.2 percentage points; P = .003). In expansion states that provided dental benefits, compared with nonexpansion states that provided dental benefits, the expansion was associated with increases in rates of Medicaid coverage (8.2 percentage points; 95%Cl 0.5 to 15.8 percentage points; P = .04) and having seen a dentist in the previous year (11.4 percentage points, 95% CI, 3.7 to 19.1 percentage points; P = .006) and decreases in the uninsured rate (-12.6 percentage points, 95% CI -18.9 to -6.4 percentage points; P < .001) and prevalence of untreated decayed teeth (-16.8 percentage points; 95% CI, -25.5 to -8.0 percentage points; P = .001). In states without Medicaid dental benefits, the expansion was associated with an increase in the mean number of missing teeth (1.3 teeth; 95% CI 0.1to 2.5 percentage points; P = .04) and a decrease in the prevalence of functional dentition (-8.7 percentage points; 95% CI, -14.1to -3.3 percentage points; P = .003) compared with nonexpansion states. CONCLUSIONS AND RELEVANCE This study found that the combination of Medicaid expansion and coverage of Medicaid dental benefits was associated with improved oral health among low-income adults.